JP3148386B2 - Dry spinning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry spinning method in which a polymer solution is spun from a spinneret into a gas to form a yarn, and more particularly, to cooling of a spun yarn and solvent evaporation in the dry spinning method. About the method.

[0002]

2. Description of the Related Art As a method of cooling a spun yarn or evaporating a solvent in dry spinning, a method of blowing a gas at a constant temperature from a direction perpendicular to the spun yarn, or a method of flowing a gas parallel to the spun yarn. Etc. are known. In that case, cooling or solvent evaporation is usually performed by a one-stage gas flow. On the other hand, the mechanism of the yarn forming process in dry spinning is complicated and has not been clarified in many points, but it is considered that evaporation of the solvent and thinning and densification of the yarn are important. From such a viewpoint, the conventional cooling or solvent evaporation method is not sufficient in terms of densification of the structure and efficient solvent evaporation, and specifically, may impair the expression of yarn physical properties, particularly strength. there were.

[0003]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present inventors have aimed at improving the physical properties of fibers, specifically, cooling or solvent evaporation which simultaneously satisfies both densification of the yarn structure and efficient evaporation. As a result of intensive studies on the method, it has been found that the thread properties can be improved by using a novel cooling or solvent evaporation method, and that the solvent can be efficiently evaporated, and the present invention has been accomplished.

[0004]

That is, the present invention relates to a dry spinning method in which an ultrahigh molecular weight polyethylene polymer solution is spun from a spinneret into a gas to form a yarn. It is intended to provide a dry spinning method characterized by improving the breaking strength of the fiber obtained by spraying from a direction perpendicular to the target and increasing the temperature of the gas flow from the spinneret side toward the later stage.

In dry spinning, the solidification (or thinning) of the spun yarn proceeds simultaneously with the evaporation of the solvent, and in some cases, the structure is not suitable for exhibiting physical properties, or the solvent evaporation efficiency is poor. Was sometimes seen. The present inventors have considered that the reason for this is that the solvent is evaporated in one step immediately after spinning, so that the compactness of the structure is reduced and the physical properties are reduced. When searching for a new cooling or solvent evaporation method that does not cause a decrease in the compactness of this structure, the spun yarn is rapidly cooled by the first-stage gas flow having a low temperature, and the solidification of the yarn is promoted. It has been found that the fiber properties are improved by efficiently promoting the evaporation of the solvent with the second and subsequent gas flows having a higher temperature than the first stage. Although the mechanism is not clear, it may be because the yarn is made denser by not evaporating the solvent positively in the first stage, and the solvent can be positively evaporated in the high temperature zone after the second stage. is expected. In other words, the present invention is a completely novel method in which the solidification of the spun yarn and the evaporation of the solvent are performed in a well-balanced manner by two or more stages of gas flows satisfying the higher condition as the temperature of the gas flow becomes higher from the spinneret side.

[0006] The dry spinning in the present invention is a general term for a method of forming a fiber by spinning a polymer solution from a spinneret into a gas, and is not limited to a polymer type and a solvent type. Examples of the polymer include polyacrylonitrile, polyurethane, polyurethane urea, polyethylene, and polyvinyl alcohol. The cooling of a spun yarn and a solvent characterized by satisfying a condition that a gas flow having two or more stages of different temperatures is blown from a substantially right angle direction and the temperature of the gas flow is higher from the spinneret side to a later stage. The evaporation method will be described in detail.

[0007] The gas flow having two or more different temperatures refers to a gas flow supplied from two or more independent outlets in a cooling or solvent evaporating apparatus generally used in a fiber production process. . The gas flow generators may be common or independent, but the temperatures supplied through independent temperature regulators (such as so-called heat exchangers) need to be different. In addition, the substantially perpendicular direction can be given a certain angle from the viewpoint of cooling efficiency and the heat retaining effect of the spinneret, indicating that it is not a cooling or solvent evaporation method in which a gas flow is made parallel to the yarn. It's just that. Before reaching the gas flow outlet, a plurality of conventionally known perforated plates and the like can be introduced and rectified.

[0008] The temperature of the gas flow must be set higher from the spinneret side to the subsequent stage. Specifically, the temperature difference between the first stage and the final stage (hereinafter referred to as ΔT) is preferably 5
The temperature must be 0 ° C or higher, more preferably 75 ° C or higher. On the other hand, if the number of stages is too large, the equipment cost will increase, which is not preferable. Therefore, a two-stage or three-stage gas flow is practically preferable. In order to achieve the object of the present invention, the first stage is to blow a gas flow having a temperature lower than the solvent boiling point of the polymer solution, and the second and subsequent stages are sprayed with a gas flow having the solvent boiling point or higher.

The wind speed of the gas stream used here needs to be optimized by the applied dry spinning method. However, the object of the present invention is to promote the solidification of the yarn and to efficiently dry the yarn. Preferably 0.5 m / s or more, more preferably 1.0 m / s or more is recommended.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples unless it exceeds the gist.

[0011]

[0012]

[0013]

EXAMPLE 1 Ultra high molecular weight polyethylene 10 having a viscosity average molecular weight of 2.6 million
Parts by weight and 90 parts by weight of decahydronaphthalene were mixed, extruded from a spinneret having an orifice having a diameter of 0.5 mm by a screw extruder set at an inlet side of 150 ° C. and an outlet side of 200 ° C., and extruded at a take-up speed of 50 m / min. Was. In addition, the extruded yarn is moved to the first stage 25.
Cooling and solvent evaporation were performed in a two-stage gas flow at 100 ° C. and a second stage. The obtained yarn was drawn under a heated gas. The obtained stretched product exhibited high strength and a high elastic modulus of 48 g / d and an elastic modulus of 1700 g / d.

Comparative Example 1 Spinning was carried out in the same manner as in the Example, except that the solvent was evaporated by a single-stage gas flow at 100 ° C. The obtained stretched material has a strength of 37 g /
d, the elastic modulus was 1200 g / d, which was inferior to the physical properties in Examples.

[0015]

According to the dry spinning method of spinning a polymer solution into a gas from a spinneret of the present invention to form a yarn,
A method of cooling a spun yarn and evaporating a solvent, characterized in that gas flows having different temperatures in the stages or more are blown from a substantially right angle direction, and the temperature of the gas flow satisfies a condition higher from a spinneret side to a later stage side. As a result, a fiber having better physical properties than conventionally known methods can be obtained.

Claims (1)

(57) [Claims] In a dry spinning method in which an ultrahigh molecular weight polyethylene polymer solution is spun from a spinneret into a gas to form a yarn, gas flows at two or more stages having different temperatures are blown from substantially perpendicular directions. Dry spinning method, wherein the breaking strength of the obtained fiber is improved by increasing the temperature from the spinneret side to the subsequent stage.